The present invention is directed to a voltage-controlled microwave oscillator having a field effect transistor as an amplifier and having a varactor diode as a frequency-determining element.
Voltage-controlled microwave oscillators are known in the prior art. In such a VCO (voltage-controlled oscillator), a voltage-variable reactance, for example a capacitance diode is connected into the frequency-determining element of the oscillator. In order, namely, to synchronize the frequency of an oscillator with the frequency of another oscillation, the oscillator frequency must be varied by a DC voltage.
Known voltage-controlled microwave oscillators also contain silicon bipolar transistors or field effect transistors (FET) as an active component (negative resistance) in addition to Gunn diodes or Impatt diodes. Because relatively few bipolar transistors work efficiently at frequencies above 12 GHz, GaAs field effect transistors are employed for use for frequencies in a range from approximately 8 GHz through 12 GHz (what is referred to as the X-band). Given such FET oscillators, for example, an inductance is connected in series between a (variable capacitance) varactor diode and the gate electrode of the FET in order to obtain an oscillatory structure. Such oscillators, however, are relatively load-sensitive.